A human heart has four chambers, the left and right atrium and the left and right ventricles. The chambers of the heart alternately expand and contract to pump blood through the vessels of the body. The cycle of the heart includes the simultaneous contraction of the left and right atria, passing blood from the atria to the left and right ventricles. The left and right ventricles then simultaneously contract forcing blood from the heart and through the vessels of the body. In addition to the four chambers, the heart also includes a check valve at the upstream end of each chamber to ensure that blood flows in the correct direction through the body as the heart chambers expand and contract. These valves may become damaged, or otherwise fail to function properly, resulting in their inability to properly close when the downstream chamber contracts. Failure of the valves to properly close may allow blood to flow backward through the valve resulting in decreased blood flow and lower blood pressure.
Mitral regurgitation is a common variety of heart valve dysfunction or insufficiency. Mitral regurgitation occurs when the mitral valve separating the left coronary atrium and the left ventricle fails to properly close. As a result, upon contraction of the left ventricle blood may leak or flow from the left ventricle back into the left atrium, rather than being forced through the aorta. Any disorder that weakens or damages the mitral valve can prevent it from closing properly, thereby causing leakage or regurgitation. Mitral regurgitation is considered to be chronic when the condition persists rather than occurring for only a short period of time.
Regardless of the cause, mitral regurgitation may result in a decrease in blood flow through the body (cardiac output). Correction of mitral regurgitation typically requires surgical intervention. Surgical valve repair or replacement is carried out as an open heart procedure. The repair or replacement surgery may last in the range of about three to five hours, and is carried out with the patient under general anesthesia. The nature of the surgical procedure requires the patient to be placed on a heart-lung machine. Because of the severity/complexity/danger associated with open heart surgical procedures, corrective surgery for mitral regurgitation is typically not recommended until the patient's ejection fraction drops below 60% and/or the left ventricle is larger than 45 mm at rest.
In some instances, patients who are suffering from mitral regurgitation are also in need of an aortic valve replacement. Studies have shown, for example, that about 30% of patients who are in need of an aortic valve replacement also have moderate to sever mitral regurgitation. Typically, these patients only receive an aortic valve replacement, and the mitral regurgitation is not treated. One method of aortic valve replacement includes trans-apical aortic valve. A trans-apical aortic valve replacement may be delivered via a trans-apical approach which utilizes a short incision (e.g., 3-4 inch long) between two ribs to gain access to the apex of the left ventricle. This is sometimes referred to as a “mini-thoracotomy,” and is much less invasive than the traditional method of getting access to the heart; a median sternotomy which involves cracking the sternal bone in the middle and spreading the chest wide open.
Another common heart condition includes coronary artery disease which may be treated by coronary artery bypass graft (CABG) surgery via a mini-thorcotomy. Sometimes such patients can also benefit from concomitant mitral repair. In fact, sometimes the patient has mitral regurgitation because of the coronary blockage, and CABG alone is not enough to treat the mitral regurgitation.
Accordingly, there exists a need to treat mitral regurgitation, particularly using a trans-apical approach.